MECHANICAL BEHAVIOUR OF THREE-UNIT ZIRCONIA INFRASTRUCTURES WITH MODIFIED COPINGS

Abstract

Aim of the study The purpose of this in vitro study was to analyse the influence of various types zirconia copings on flexural strength of zirconia frameworks designated for posterior tooth-supported fixed dental prostheses. Materials and methods Zirconia samples (Pre-sintered Zirconia, 3Y-TZP, NOVAZir® ST, Novadent, Hamburg, Germany) were designed as three-unit bridge infrastructures, replacing the first right lower molar. The samples (n=4) were divided into two testing groups: the first group included two samples with copings having even thickness of 0.6mm (coded P1 and P2), and second group (coded P3 and P4) comprised modified copings with thickness varying from 0.80-0.84mm in specific occlusal-axial areas. The cross sectional area of all connectors was established at 9mm² with an elliptical shape. Mechanical tests (three-point flexural tests) were conducted on all samples using a universal testing machine. Results The evaluation of zirconia samples’ mechanical behaviour revealed group-depended differences: zirconia samples with modified copings demonstrated higher flexural strength in the applied mechanical tests (0.894kN for P3 and 1.109kN for P4) compared to zirconia samples with even coping thickness (0.561kN for P1 and 0.772kN for P2). Conclusions Modified zirconia copings have shown potential as an alternative to enhance the flexural strength of zirconia infrastructures, and could provide a more suitable support and an even thickness for veneering ceramic.

Keywords

• zirconia
• modified copings
• flexural strength
• dental prosthesis
• cad-cam